The present invention relates to the moulding of ceramics articles by introducing into a mould cavity of a pressing mould defined by at least two relatively movable mould sections a body of ceramics clay, closing the mould by moving the mould sections under pressure to positions corresponding to the outlines to be moulded, opening the mould and removing the now moulded body of clay and passing the moulded body to further processing.
Various modifications of such procedures are known and applied in ceramics manufacture. In the manufacture of crockery for example, cups are usually manufactured e.g. by the modification known as "jigger moulding" in which the body of clay is first pre-shaped in the mould prior to the closing of the mould and final pressing of the articles.
In conventional moulding procedures, the dies of the mould are heated to a high temperature to facilitate the release of the clay from the mould due to the formation of steam. The need for such heating is a disadvantage for which reason smaller articles, e.g. the handles of cups and similar articles of crockery, have been manufactured in the past by different methods, e.g. slipcasting.
Because the shrinkage of handles so produced is different from that of the cup or the like produced by pressure moulding, there is a considerable tendency for these handles to come loose in subsequent manufacture. Conventionally produced handles furthermore require (usually manual) shaping and trimming of the contact faces by which the handles are joined to the cup or other item of crockery.
In slip-casting a slip of clay is cast into a plaster of Paris mould. The porous plaster of Paris absorbs water from the slip. The moulded article, because of its loss of water to the mould shrinks and is thereby readily released by the mould. With this in mind, attempts were made to apply this principle to a wet pressing method, by inserting a layer of an absorbent, i.e. moisture pervious material such as blotting paper between the clay and the surface of the pressing die (the latter being made of metal). These attempts were not satisfactory.
Disclosed is a process which in the appropriate circumstances facilitates the manufacture of ceramics articles. In particular the process is adaptable to the manufacture of comparatively small articles such as the handles of cups and similar items of crockery. The process is adaptable to largescale manufacture and can be adapted to eliminate also the inconvenient prior step of shaping and trimming the contact faces of crockery handles. In addition there is provided an apparatus for carrying out the process.